The statements in this section merely provide background information related to the present disclosure and may not constitute prior art.
In general, D-range neutral control logic and auto hold logic, applied to an automatic transmission vehicle in order to improve the marketability thereof, have different functions. Here, logic means a mode or a method. Also, idle NVH in D-range and idle NVH in N-range represent idle noise.
D-range neutral control logic may greatly improve the marketability of a vehicle with regard to NVH by refining idle NVH in an automatic transmission vehicle, in which NVH during idle in D-range is more severe than NVH during idle in N-range.
This is because D-range requires the increase of a load on an engine due to direct engagement to the torque converter of an automatic transmission, which increases fuel consumption, but N-range prevents the load of the torque converter of the automatic transmission from being applied, which decreases fuel consumption. Accordingly, when conditions for neutral control are satisfied in D-range, an N-range idle state, in which less fuel is consumed compared to a D-range idle state, is used, whereby a refined idle NVH level in N-range may be realized also in D-range.
Auto hold logic maintains an idle state even when a driver takes his or her foot off a brake pedal during idle in D-range. Accordingly, auto hold logic may reduce driver's fatigue whereby the driver does not have to keep his or her foot on a brake pedal when frequently entering an idle state while driving in urban areas, thereby improving driver's convenience.
Therefore, an automatic transmission vehicle may improve marketability with regard to idle NVH by performing D-range neutral control when entering an idle state, and may also improve driver's convenience through auto hold logic when entering an idle state.
However, because both D-range neutral control logic and auto hold logic use a brake pedal effort (i.e. a pedal stroke) as the common factor of idle control, auto hold control may intervene in D-range neutral control, which may cause the effect of idle NVH refinement, achieved through D-range neutral control, to change.
For example, when a driver does not manipulate a brake according to an auto hold condition, this is recognized as dissatisfying a condition for D-range neutral control, which cancels D-range neutral control. As a result, a driver feels that NVH is refined when D-range neutral control is performed during idle, but feels that NVH is deteriorated when auto hold control is performed during idle. Such a change of NVH during idle may result in customer complaints about the vehicle.